U.S. patent application number 09/290176 was filed with the patent office on 2001-11-15 for method for chamfering a wafer.
This patent application is currently assigned to NISHI AND MURAI. Invention is credited to MURAI, SHIROU, NISHI, KENICHIRO.
Application Number | 20010041513 09/290176 |
Document ID | / |
Family ID | 26390813 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010041513 |
Kind Code |
A1 |
NISHI, KENICHIRO ; et
al. |
November 15, 2001 |
METHOD FOR CHAMFERING A WAFER
Abstract
In the wafer chamfering method, there is used a disk-shaped
grindstone 8 which includes: a peripheral edge portion serving as a
grinding surface 1; a flat portion formed in the central portion of
the grinding surface 1 in the width direction thereof; and, two
edge portions 5 respectively formed on the two sides of the flat
portion 2 in the width direction thereof and made in the form of
the shape of the valley portion of the notch portion 4 of a
disk-shaped wafer 3 to be chamfered. In operation, in the wafer
chamfering method, while rotating the above grindstone 8, the
grindstone 8 is revolved in the thickness direction of the wafer 3
to thereby chamfer the wafer 3. Especially, the present wafer
chamfering method comprises two steps: that is, a circumferential
portion grinding step in which the grindstone is supported such
that it stands upright or at right angles to the circumferential
portion 6 of the wafer 3 at their respective mutual contact points
and only the flat portion of the grindstone 8 is contacted with the
mutual contact points to thereby chamfer the peripheral edge
portion of the wafer 3; and, a notch portion grinding step in which
the grindstone is supported such that it is inclined with respect
to the diameter direction of the notch portion of the wafer 3 by an
angle of about 45.degree. in the circumferential direction of the
wafer 3 and the edge portions 5 or both of the edge portions 5 and
flat portion 2 are used to chamfer the notch portion 4 of the wafer
3.
Inventors: |
NISHI, KENICHIRO; (KANAGAWA,
JP) ; MURAI, SHIROU; (TOYAMA, JP) |
Correspondence
Address: |
SUGHRUE MION ZINN MACPEAK & SEAS
2100 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
200373202
|
Assignee: |
NISHI AND MURAI
|
Family ID: |
26390813 |
Appl. No.: |
09/290176 |
Filed: |
April 13, 1999 |
Current U.S.
Class: |
451/44 ;
257/E21.237 |
Current CPC
Class: |
B24D 5/02 20130101; H01L
21/02021 20130101; B24B 9/065 20130101 |
Class at
Publication: |
451/44 |
International
Class: |
B24B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 13, 1998 |
JP |
HEI. 10-101267 |
Feb 26, 1999 |
JP |
HEI. 11-050348 |
Claims
What is claimed is:
1. A wafer chamfering method comprising the steps of: chamfering a
peripheral edge portion of a disk-shaped wafer while rotating a
disk-shaped grinding wheel and revolving around said peripheral
edge portion of said disk-shaped wafer in a width direction thereof
under conditions that a first plane substantially containing said
disk-shaped wafer is substantially extended perpendicular to a
second plane substantially containing said disk-shaped grinding
wheel and that said second plane is substantially contained in a
third plane which is defined by containing a diameter of said wafer
and substantially extending perpendicular to said first plane.
2. The wafer chamfering method according to claim 1, further
comprising the steps of: forming a notch portion on said
disk-shaped wafer while rotating said grind wheel under conditions
that said first plane is substantially extended perpendicular to
said second plane and that said second plane is inclined with
respect to said third plane by an predetermined angle.
3. The wafer chamfering method according to claim 2, in which said
second plane is inclined with respect to said third plane by an
angle of about 45.degree. when said notch portion is formed.
4. The wafer chamfering method according to claim 1, in which said
disk-shaped grinding wheel comprises: a disk-shaped grindstone
including a circumferential portion in which a flat portion for
chamfering said peripheral edge portion of said wafer is formed in
its central portion in said width direction.
5. The wafer chamfering method according to claim 4, in which said
disk-shaped grindstone further including: at least one of edge
portions formed in adjacent to said flat portion in the width
direction, each having a shape mating with a part of said notch
portion so as to form a valley part of said notch portion.
6. The wafer chamfering method according to claim 5, in which said
notch portion is simultaneously formed by said flat portion and
said edge portions.
7. The wafer chamfering method according to claim 2, in which said
disk-shaped grinding wheel comprises: a first disk-shaped
grindstone member having a flat portion for chamfering said
peripheral edge portion of said wafer; and a second disk-shaped
grindstone member attached to said first disk-shaped grindstone
member and having an edge portion in the form of a shape mating
with a part of said notch so as to form a valley part of said notch
portion.
8. The wafer chamfering method according to claim 7, in which said
first and second disk-shaped grindstone member are integrally
formed.
9. The wafer chamfering method according to claim 1, in which the
peripheral speed of said wafer thus rotated is set higher than or
equal to 100 m/min.
10. The wafer chamfering method according to claim 2, in which the
peripheral speed of said wafer thus rotated is set higher than or
equal to 100 m/min.
11. The wafer chamfering method according to claim 7, in which the
peripheral speed of said wafer thus rotated is set higher than or
equal to 100 m/min.
12. The wafer chamfering method according to claim 1, in which a
ratio of the peripheral speed of said grindstone to the peripheral
speed of said wafer is set in the range of 0.001-10.
13. The wafer chamfering method according to claim 2, in which a
ratio of the peripheral speed of said grindstone to the peripheral
speed of said wafer is set in the range of 0.001-10.
14. The wafer chamfering method according to claim 7, in which a
ratio of the peripheral speed of said grindstone to the peripheral
speed of said wafer is set in the range of 0.001-10.
15. The wafer chamfering method according to claim 9, in which a
ratio of the peripheral speed of said grindstone (8) to the
peripheral speed of said wafer is set in the range of 0.001-1.
16. The wafer chamfering method according to claim 10, in which a
ratio of the peripheral speed of said grindstone to the peripheral
speed of said wafer is set in the range of 0.001-1.
17. The wafer chamfering method according to claim 11, in which a
ratio of the peripheral speed of said grindstone to the peripheral
speed of said wafer is set in the range of 0.001-1.
18. The wafer chamfering method according to claim 1, further
comprising the steps of: executing an operation for grinding one of
end faces of said wafer continuously.
19. The wafer chamfering method according to claim 2, further
comprising the steps of: executing an operation for grinding one of
end faces of said wafer continuously.
20. The wafer chamfering method according to claim 7, further
comprising the steps of: executing an operation for grinding one of
end faces of said wafer continuously.
21. The wafer chamfering method according to claim 9, further
comprising the steps of: executing an operation for grinding one of
end faces of said wafer continuously.
22. The wafer chamfering method according to claim 14, further
comprising the steps of: executing an operation for grinding one of
end faces of said wafer continuously.
23. The wafer chamfering method according to claim 15, further
comprising the steps of: executing an operation for grinding one of
end faces of said wafer continuously.
24. The wafer chamfering method according to claim 2, in which said
disk-shaped grindstone including: at least one edge portion formed
at one end of the circumferential portion thereof in the width
direction, each having a shape mating with a part of said notch
portion so as to form a valley part of said notch portion.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a wafer chamfering method
for working the peripheral edge portion of a semiconductor wafer,
particularly, relates to a wafer chamfering method for working the
peripheral edge portion of a semiconductor wafer into a convexly
curved surface shape using a disk-shaped grindstone.
[0002] Conventionally, in a process for manufacturing a
semiconductor device, in order to be able to facilitate the
matching of the crystal orientation of a semiconductor wafer, in
the peripheral edge of the wafer, there is formed an orientation
flat which can be produced by cutting linearly part of the
peripheral edge of the wafer, or a notch portion which can be
produced by cutting part of the peripheral edge of the wafer in a
substantially V-like or arc-like shape. Especially, the
substantially V-shaped notch portion is most often employed because
the V-shaped notch portion makes it possible to make efficient use
of the limited area of the wafer and also can provide excellent
positioning precision.
[0003] In the conventional semiconductor device manufacturing
process, not infrequently, the peripheral edge of the semiconductor
wafer is accidentally contacted with part of a device which is used
in the semiconductor device manufacturing process. Such contact
sometimes produces fragments or tips which are causes to
deteriorate the quality of the semiconductor device. Therefore, it
is necessary to chamfer the peripheral edge of the semiconductor
wafer and, today, a wafer chamfering operation is generally
employed in the semiconductor device manufacturing process.
[0004] Conventionally, to form a curved surface in the peripheral
edge portion of a wafer, the rotational axis of a grindstone is
moved in the thickness direction of the wafer along an orbit
selected in consideration of the shape of the wafer peripheral edge
portion after chamfered, such as a circular orbit around the
peripheral edge portion of the wafer. And, in this operation, the
grindstone is solely contacted with the peripheral edge of the
wafer in such a manner as shown in FIG. 13, that is, the grindstone
is supported such that it stands up straight or at right angles to
the peripheral edge portion of the wafer at their mutual contact
points, while the grinding surface of the grindstone is formed
relatively sharp in order to be able to grind the notch portion of
the wafer which is small in area. Therefore, it is inevitable that,
in use, the sharp or tapered grinding surface of the grindstone can
be worn or abraded and thus flattened in a short period of
time.
[0005] Also, since, in the notch portion, the thickness of the
grindstone is limited so as to be able to provide the sharp portion
thereof as large as possible, from the viewpoint of strength, only
the grindstone having a small diameter (that is, having a small
circumference) can be used. Further, such small-diameter grindstone
is not able to enhance the working efficiency thereof unless it is
rotated at a very high speed, but such high-speed rotation of the
grindstone causes the grinding surface of the grindstone to lose
its predetermined allowable shape early. This is a vicious circle.
If the grinding surface of the grindstone loses its predetermined
allowable shape, then the shape of the working surface of the wafer
is influenced by the thus shape-lost or deformed grinding surface.
This raises the need to dress/adjust the deformed grinding surface
again, which in turn increases the cost of the wafer as well as the
cycle time of the wafer (that is, a unit time necessary to chamfer
the peripheral edge portion of a piece of wafer). Similarly, from
the viewpoint of preventing the grinding surface from losing its
predetermined allowable shape, in the conventional wafer chamfering
method, it is difficult that the same grindstone is commonly used
to chamfer the circumferential portion of the wafer as well as to
chamfer the notch portion thereof which is sharpened: that is, a
series of chamfering operations to be executed continuously without
replacing the grindstone cannot be applied in both of the
circumferential portion and notch portion of the wafer.
[0006] Further, conventionally, a so called forming grindstone (a
grindstone having a section which corresponds in shape to the shape
of a workpiece or a wafer to be chamfered) is used in the
mirror-surface working operation on the circumferential portion of
a wafer, and the forming grindstone is rotated at a high speed of
several thousands m/min. to thereby grind the circumferential
portion of the wafer into a mirror-like surface. However, to
provide such mirror-like surface, it is necessary to use a
relatively soft grindstone having a micro abrasive grains.
Therefore, the grindstone itself can be easily abraded partially to
thereby lose its shape, and the shape loss of the grindstone is
transferred to the wafer to thereby roughen the surface of the
wafer. To avoid this, the grindstone must undergo a
re-shaping/dressing operation frequently, which increases the cost
of the wafer chamfering method.
[0007] Still further, in the conventional wafer chamfering method,
because the relation between the peripheral speed of a wafer (that
is, the moving speed of the peripheral edge of the wafer obtained
as the wafer is rotated) and the peripheral speed of a grindstone
(that is, the moving speed of the peripheral edge of the grindstone
obtained as the grindstone is rotated) is not decided, grinding
streaks are often produced in such a manner as to cause cracks in
the wafer easily; and, in particular, when the peripheral speed of
a wafer is low, the wafer is damaged extremely heavily when it is
contacted with the grindstone.
[0008] Further, there is enforced a conventional method which uses
float grains (so called as slurry) to polish the wafer. With use of
this method, although the polished condition of the top surface
portion of the wafer surface can be enhanced, the surface of the
wafer cannot be finished in an arbitrary shape nor in the same
shape all the time due to the fact that the polishing is depended
upon the float grains being uncontrollable (see Japanese Patent
Unexamined Publication No. Hei. 9-168953).
SUMMARY OF THE INVENTION
[0009] The present invention aims at eliminating the drawbacks
found in the above-mentioned conventional wafer chamfering
method.
[0010] Accordingly, it is an object of the present invention to
provide a wafer chamfering method which can chamfer a surface of
wafer into an arbitrary shape and in the same shape all the time
with excellent reproduction characteristics. In the above-mentioned
object can be attained by a wafer chamfering method, according to
the present invention, comprising the steps of:
[0011] chamfering a peripheral edge portion of a disk-shaped wafer
while rotating a disk-shaped grinding wheel and revolving around
the peripheral edge portion of the disk-shaped wafer in a width
direction thereof under conditions that a first plane substantially
containing the disk-shaped wafer is substantially extended
perpendicular to a second plane substantially containing the
disk-shaped grinding wheel and that the second plane is
substantially contained in a third plane which is defined by
containing a diameter of the wafer and substantially extending
perpendicular to the first plane.
[0012] In addition, it is also an object of the invention to
provide a wafer chamfering method which can commonly use the same
grindstone in both grinding the circumferential portion of a wafer
and in chamfering the tapered notch portion of the wafer to thereby
be able not only to carry out a series of chamfering operations
without replacing the grindstone but also to use the same
grindstone for a relatively long period of time.
[0013] In the above-mentioned object can be attained by a wafer
chamfering method, according to the present invention, comprising
the steps of:
[0014] chamfering a peripheral edge portion of a disk-shaped wafer
while rotating a disk-shaped grinding wheel and revolving around
the peripheral edge circumferential portion of the disk-shaped
wafer in a width direction thereof under conditions that a first
plane substantially containing the disk-shaped wafer is
substantially extended perpendicular to a second plane
substantially containing the disk-shaped grinding wheel and that
the second plane is substantially contained in a third plane which
is defined by containing a diameter of the wafer and substantially
extending perpendicular to the first plane; and
[0015] forming a notch portion on the disk-shaped wafer while
rotating the grind wheel under conditions that the first plane is
substantially extended perpendicular to the second plane and that
the second plane is inclined with respect to the third plane by an
predetermined angle.
[0016] In the above-mentioned wafer chamfering method, according to
the present invention, it is advantageous that the second plane is
inclined with respect to the third plane by an angle of about
45.degree. when the notch portion is formed.
[0017] In the above-mentioned wafer chamfering method, according to
the present invention, it is also advantageous that the disk-shaped
grinding wheel comprises:
[0018] a first disk-shaped grindstone member having a flat portion
for chamfering the circumferential portion; and
[0019] a second disk-shaped grindstone member attached to the first
disk-shaped grindstone member and having an edge portion in the
form of a shape mating with a part of the notch so as to form a
valley part of the notch portion.
[0020] In addition, the above objects can also be achieved by a
wafer chamfering method according to the present invention, wherein
a disk-shaped grindstone is revolved, while rotating the
grindstone, in the width direction of a disk-shaped wafer to be
chamfered while the wafer is supported in a rotating manner,
thereby chamfering the wafer, the grindstone including a peripheral
edge portion serving as a grinding surface, a flat portion formed
in the central portion of the grinding surface in the width
direction thereof, and two edge portions respectively formed on the
two sides of the flat portion in the width direction thereof and
made in the form of the shape of the valley portion of a notch
portion of the wafer, the present wafer chamfering method
comprising the two following steps: that is, a circumferential
portion grinding step in which the grindstone is so supported as to
stand upright or at right angles to a circumferential portion of
the wafer at their respective mutual contact points and only the
flat portion of said grindstone is contacted with the mutual
contact points to thereby chamfer the circumferential portion of
the wafer; and, a notch portion grinding step in which the
grindstone is so supported as to be inclined with respect to the
diameter direction of the notch portion of the wafer by an angle of
about 45.degree. in the circumferential direction of the wafer, and
the edge portions or both of the edge portions and flat portion are
used to chamfer the notch portion of the wafer.
[0021] In the above-mentioned structure, "to use the peripheral
edge portion of the grindstone as the grinding surface" means that
the peripheral edge portion of the grindstone (including the
peripheral edge portions of the two end faces of the grindstone and
the peripheral surface of the grindstone) is used in a wafer
chamfering operation. However, it does not mean that only the
peripheral edge portion of the grindstone has abrasive grains.
Therefore, it is naturally possible that almost the whole of the
grindstone is made of abrasive grains. Preferably, the flat portion
of the grinding surface may be formed sufficiently wider than the
contact width of the flat portion with respect to the peripheral
edge portion of the wafer to thereby make it difficult for the
abrasion of the flat portion to have ill influences on the
above-mentioned edge portions of the grindstone. Also, the edge
portions may be molded in a curved surface shape according to the
valley portion shape of the notch portion of the wafer. Further,
"to rotate the grindstone in the thickness direction of the wafer"
means, for example, that the rotational axis of the grindstone is
arranged in parallel to the plane (surface) of the wafer.
[0022] The circumferential portion of the wafer means the
circumferential-shaped portion of the peripheral edge portion of
the wafer, that is, the other remaining portions of the peripheral
edge portion of the wafer than the notch portion thereof. "To
support the grindstone upright or at right angles to the
circumferential portion of the wafer at the respective mutual
contact points" means that not only the rotational axis of the
grindstone is arranged in parallel to the plane (surface) of the
wafer, but also the supporting direction of the grindstone is
coincident with the diameter direction of the wafer at the mutual
contact points between the grindstone and wafer. "To chamfer the
notch portion of the wafer using the edge portions or both of the
edge portions and flat portion of the grindstone" does not mean
that the notch portion is chamfered using only the edge portions
and flat portion of the grindstone, but it also includes a case in
which the adjoining portions of the edge portions and flat portion
are used in such wafer chamfering operation.
[0023] Further, the above objects can also be achieved by a wafer
chamfering method according to the present invention, wherein a
grindstone, while rotating the grindstone, is revolved in the
thickness direction of a wafer supported in a rotating manner to
thereby chamfer the wafer, the wafer chamfering method comprising
the two following steps: that is, a circumferential portion
grinding step in which, as the grindstone, there is used a
disk-shaped grindstone including a peripheral edge portion serving
as a grinding surface and at least a flat portion in the width
direction of the grinding surface is used, and the flat portion of
the grindstone is so supported as to stand upright or at right
angles to a circumferential portion of wafer at their respective
mutual contact points to thereby chamfer the circumferential
portion of the wafer; and, a notch portion grinding step in which,
as a grindstone, a grindstone including a flat portion and at least
one edge portion is used to chamfer a notch portion of the wafer,
or a grindstone including only the edge portion and a grindstone
including only the flat portion are used in combination to chamfer
the notch portion of the wafer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is an explanatory view of an embodiment of a
circumferential portion grinding step employed in a wafer
chamfering method according to the invention;
[0025] FIG. 2 is an explanatory view of an embodiment of a notch
portion grinding step employed in a wafer chamfering method
according to the invention;
[0026] FIG. 3 is an explanatory view of an embodiment of a notch
portion grinding step employed in a wafer chamfering method
according to the invention;
[0027] FIG. 4 is an explanatory view of an embodiment of the orbit
of a grindstone employed in a wafer chamfering method according to
the invention;
[0028] FIG. 5A is an enlarged view of an embodiment of the grinding
surface of a grindstone employed in a wafer chamfering method
according to the invention;
[0029] FIG. 5B is an enlarged view of a modified embodiment of a
grindstone employed in FIG. 5A.;
[0030] FIG. 6 is a schematic view of an embodiment of a
circumferential portion grinding step employed in a wafer
chamfering method according to the invention;
[0031] FIG. 7 is a schematic view of an embodiment of a notch
portion grinding step employed in a wafer chamfering method
according to the invention;
[0032] FIG. 8 is a schematic view of an embodiment of a notch
portion grinding step employed in a wafer chamfering method
according to the invention;
[0033] FIG. 9 is a perspective view of an embodiment of a wafer
after chamfered and an enlarged view of the main portions thereof
obtained in a wafer chamfering method according to the
invention;
[0034] FIG. 10A is an explanatory view of an another embodiment of
the orbit of a grindstone employed in a wafer chamfering method
according to the invention;
[0035] FIG. 10B is an explanatory view of an embodiment of the
movement of a grindstone employed in a wafer chamfering method
according to the invention;
[0036] FIG. 11 is a plan view of an embodiment of a wafer after
chamfered obtained in a wafer chamfering method according to the
invention;
[0037] FIG. 12 is a perspective view of an embodiment of a wafer
after chamfered and an enlarged view of the main portions thereof
obtained in a wafer chamfering method according to the
invention;
[0038] FIG. 13 is an explanatory view of an embodiment of a notch
portion grinding step employed in a conventional wafer chamfering
method;
[0039] FIGS. 14A-D are sectional views of modifications of a
grindstone including at least one flat portion; and
[0040] FIGS. 15A-C are sectional views of modifications of a
grindstone including at least one edge portion.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] Now, description will be given below of an embodiment of a
wafer chamfering method according to the invention, in which a
wafer is chamfered by a circumferential portion grinding step and a
notch portion grinding step in this order.
[0042] A grindstone 8, which is used to chamfer a wafer 3, has such
a disk shape as shown in FIG. 4 and includes a grindstone main body
9 which is formed by securing abrasive grains fixedly to the
peripheral edge portion of the grindstone 8. The surface of the
grindstone main body 9 is used as a grinding surface 1: in
particular, in the grinding surface 1, in the width-direction
central portion of the peripheral surface 10 of the grindstone 8,
there is formed a flat portion 2 and, at the positions of the
grinding surface 1 that are respectively located in the
neighborhood of the boundary between the peripheral surface 10 of
the grindstone 8 and the end faces 11 thereof and correspond to the
width-direction two sides of the flat portion 2, there are formed
two edge portions 5 which are respectively made in the shape of the
valley portion shape of the notch portion 4 of the wafer 3 to be
chamfered (see FIG. 5A). By the way, as the grindstone 8, it is
preferred to use a grindstone which has a diameter in the range of
50-200 mm.
[0043] The grindstone 8 is disposed in such a manner that its
rotational axis P intersects at right angles to the center axis O
of the wafer 3 (that is, the rotation axis P extends in parallel to
the plane of the wafer 3), and thus, in operation, the grinding
surface 1 of the grindstone 8 is able to grind the peripheral edge
portion of the wafer 3 while moving in the thickness direction of
the wafer 3 (that is, while the grindstone 8 is rotating about the
rotational axis P in the thickness direction of the wafer 3).
Referring in particular to an operation to chamfer the peripheral
edge portion of the wafer 3, the diameter of the grindstone 8 and a
curvingly-shaped orbit Q for the movement of the rotational axis P
of the grindstone 8 are respectively set so as to correspond to the
section shape of the peripheral edge portion of the wafer 3 after
chamfered, and the rotational axis P of the grindstone 8 is moved
in the thickness direction of the wafer 3 along the orbit Q (see
FIG. 4) in every portion of the peripheral edge portion of the
wafer 3, thereby chamfering the peripheral edge portion of the
wafer 3 in a curved manner. And, in the present embodiment, a
support base (not shown) is rotated through a rotary shaft secured
to a given position, and the disk-shaped wafer 3, which is fixedly
secured on the support base and has an almost circular shape, is
rotated to thereby chamfer the wafer 3 over the whole peripheral
edge portion thereof.
[0044] In another embodiment, as shown in FIG. 10A, that is, in a
case in which the peripheral edge portion of the wafer 3 is
chamfered in a circumferential shape, the diameter of the
grindstone 8 and the rotational axis P of the grindstone 8 are
respectively set so as to correspond to the curvature of the wafer
peripheral edge portion after chamfered, and the rotational axis P
of the grindstone 8 is moved in the thickness direction of the
wafer 3 in every portion of the peripheral edge portion of the
wafer 3 along a circular orbit CO having its center at a position
which can be obtained by the thus set grindstone 8 diameter and the
moving radius of the rotational axis P, thereby being able to
chamfer the peripheral edge portion of the wafer 3 in a
circumstantial shape. And, as shown further in FIG. 10B, if the
grindstone 8 is moved linearly along the end face 11 of the wafer
3, then the peripheral edge portion and end face 11 of the wafer 3
can be ground into a mirror-like surface in the same step, which in
turn can enhance the efficiency of the grinding operation as
well.
[0045] In other words, in the warder chamfering method according to
the present invention, a circumferential portion 6 of a disk-shaped
wafer 3 is chamfered while rotating a disk-shaped grinding wheel 8
and revolving around the circumferential portion 6 of the
disk-shaped wafer 3 in a width direction thereof under following
conditions (i) and (ii):
[0046] (i) a first plane FP substantially containing the
disk-shaped wafer 3 is substantially extended perpendicular to a
second plane SP substantially containing the disk-shaped grinding
wheel 8; and
[0047] (ii) that the second plane SP is substantially contained in
a third plane TP which is defined by containing a diameter of the
wafer and substantially extending perpendicular to the first plane
FP (Refer FIGS. 1 and 3).
[0048] The circumstantial portion grinding step is an operation in
which, as shown in FIGS. 1 and 6, the grindstone 8 is supported
such that it stands upright or at right angles to the
circumferential portion 6 of the wafer 3 (along the diameter
direction thereof) at their respective mutual contact points, and
only the flat portion 2 of the grindstone 8 is contacted with the
circumferential portion 6 of the wafer 3 to thereby chamfer the
circumferential portion 6 of the wafer 3.
[0049] On the other hand, the notch portion grinding step is an
operation in which, as shown in FIGS. 2 to 3 or 7 to 8, the
grindstone is supported such that it is inclined with respect to
the diameter direction of the notch portion 4 of the wafer 3 by an
angle of about 45.degree. in the circumferential direction of the
wafer 3, and the edge portions 5 and flat portion 2 are used to
chamfer the notch portion 4 of the wafer 3. Referring here to the
attitude of the grindstone when it is used to grind the wafer,
generally, the grindstone is supported in such a manner that it
stands upright or at right angles to the circumferential portion of
the wafer at their respective mutual contact points. However, the
attitude of the grindstone is not limited to such attitude but, for
example, the grindstone can also be supported in such a manner that
the rotational axis of the grindstone is parallel to the rotational
axis of the wafer. By the way, the grindstone can also be used to
grind one of the end faces of the wafer continuously.
[0050] Note that, in other words, as shown in FIGS. 2 and 3, in the
warder chamfering method according to the present invention, a
notch portion on the disk-shaped wafer is formed while rotating the
grind wheel 8 under following conditions (iii) and (iv):
[0051] (iii) the aforementioned first plane is substantially
extended perpendicular to the aforementioned second plane;
[0052] (iv) that the aforementioned second plane is inclined with
respect to the aforementioned third plane by an predetermined angle
(for example, about 45 degree).
[0053] When the circumstantial portion grinding step is carried
out, the flat portion 2 of the grinding surface 1 of the grindstone
8 is worn or abraded in a curvedly recessed manner after the shape
of the circumferential portion of the wafer 3 and, if the width of
the flat portion 2 is excessively small, then the shapes of the
edge portions 5 of the grinding surface 1 are also caused to change
due to the abraded flat portion 2, which makes it impossible to
make effective use of the grindstone 8. On the other hand, if the
flat portion 2 is formed in a long shape, when using the flat
portion 2, by moving the grindstone 9 slightly and reciprocatingly
in the direction of the rotational axis P, the amount of abrasion
of the flat portion 2 in a given portion can be reduced; and also,
by moving the flat portion 2 sequentially while avoiding the
abraded portion(s) thereof, there can be obtained a similar effect
to the above.
[0054] In the present circumferential portion grinding step, the
wafer 3 is rotated in such a manner that the peripheral speed of
the wafer 3 provides 100 m/min. or higher at least in a finishing
step (for example, when the wafer 3 is ground in the order of a
rough grinding operation, intermediate grinding operation, and a
precision grinding operation, the finishing step corresponds to the
precision grinding operation), and also the grindstone 8 is
revolved while it is rotating. By grinding the wafer 3 under these
chamfering conditions, in the circumferential portion 6 of the
wafer 3, as shown in FIG. 12, there can be produced a grinding
streak 12 which flows in the radial direction of the wafer 3 from
the center thereof. Further, if the ratio of the peripheral speed
of the grindstone 8 to the peripheral speed of the wafer 3 is set
in the range of 0.001-10, then, in the circumferential portion 6 of
the wafer 3, as shown in FIG. 9, there can be produced a grinding
streak 13 which extends along the direction of a concentric circle
of the wafer 3. That is, this makes it possible to prevent more
effectively the damage of the wafer 3 such as a crack and the like
from spreading up to the central portion of the wafer 3.
[0055] Here, the expression "the ratio of the peripheral speed of
the grindstone 8 to the peripheral speed of the wafer 3" means the
peripheral speed of the grindstone (that is, the moving speed of
the peripheral edge of the grindstone produced by the rotation of
the grindstone)/the peripheral speed of the wafer (the moving speed
of the peripheral edge of the wafer produced by the rotation of the
wafer). In particular, if the ratio of the peripheral speed of the
grindstone 8 to the peripheral speed of the wafer 3 is less than
0.001, then the abrasive grains can be removed or abraded easily to
thereby make it difficult to grind the wafer. That is, it is not
desirable to select such low peripheral speed ratio. On the other
hand, if the peripheral speed ratio is set in the range of 0.001-1,
then the damage of the wafer 3 can be prevented further
effectively. Further, as described above, if the grindstone 8 is
moved linearly along the end face 11 of the wafer 3, as shown in
FIG. 11, the grinding streak to be produced in the end face 11 of
the wafer 3 can be made to extend along the direction of a
concentric circle of the wafer 3, which can enhance the wafer
damage preventive effect still further. By the way, the above
setting of the peripheral speeds of the grindstone and wafer may be
preferably employed at least in the finishing step (for example,
when the wafer 3 is ground in the order of a rough grinding
operation, intermediate grinding operation, and a precision
grinding operation, the finishing step corresponds to the precision
grinding operation). However, a timing of the chamfering operation
in which a peripheral speed ratio setting should be employed may be
selected properly according to the procedures of the actual
chamfering operations.
[0056] The above-mentioned working or grinding condition that the
peripheral speed of the wafer 3 is set higher than or equal to 100
m/min. can provide the following effects: that is, it can
supplement/compensate the limited area of instantaneous contact
between the grindstone 8 and wafer 3 in the grinding operation, can
secure a sufficient contact area per unit time between them to be
accumulated due to the rotation thereof, and can enhance the
efficiency of the grinding operation. From the viewpoint of
attaining the above effects, preferably, the peripheral speed of
the wafer 3 may be set higher than or equal to 200 m/min., and,
more preferably, it may be set higher than or equal to 300 m/min.
By the way, the above-mentioned working condition that the rotation
direction of the grindstone 8 is set in a single direction aims at
eliminating as much as possible the factors that give rise to
various grinding streaks in the wafer and, especially, it is
desirable to employ this working condition in preventing the
grinding streaks that could be otherwise produced due to the
inverted rotation of the grindstone 8.
[0057] Also, as the notch portion grinding operation is repeated,
the abrasion of the edge portion 5 also progresses; but, due to the
abrasion of the flat portion 2 caused by the above-mentioned
circumferential portion grinding step, there is formed a new edge
portion following the edge portion 5 that has been abraded to
disappear, although the new edge portion is different in curvature
from the old edge portion 5: that is, such formation of the new
edge portion makes it possible to extend the life of the grindstone
8.
[0058] The plane shape of the notch portion 4 that can be chamfered
depends on the shape of the grinding surface 1 of the grindstone 8
and, in particular, the notch portion 4 having an angle larger than
or equal to the angle that is formed by the peripheral surface 10
and end face 11 of the grindstone 8 (which is hereinafter referred
to as an edge angle) can be chamfered. Therefore, if the edge angle
is set as an acute angle, the cut-away portion of the notch portion
4 can be reduced; but, from the viewpoint of prevention of the
notch portion 4 of the wafer 3 against breakage, preferably, the
edge angle may be rather set as an obtuse angle, while the obtuse
edge angle is also advantageous in strength. However, if the edge
angle is set as an excessively obtuse angle, then there can be lost
the advantages of the shape of the notch portion 4 having a V-like
shape, such as the efficient use of the limited area of the wafer
3, excellent positioning precision and the like. With the above
facts taken into account, from the viewpoint of stable use of the
area of the portion that provides the grinding surface 1 and thus
from the viewpoint of stable use of the shape of the notch portion
4, most preferably, the edge angle may be set about 90.degree..
[0059] By the way, the above-mentioned embodiments are not
limitative but, according to the invention, other embodiments are
also possible. For example, an embodiment in which, in the
circumferential portion grinding step thereof, a grindstone
including at least a flat portion 2 formed in the width direction
of the grinding surface 1 thereof is used as shown in FIGS. 14A,
14B, 14C and 14D; an embodiment in which, in the notch portion
grinding step thereof, a grindstone including a flat portion 2 and
at least one edge portion 5 is used as shown in FIGS. 15A, 15B and
15C; and, an embodiment in which, a grindstone including only the
edge portion and a grindstone including only the flat portion are
used in combination to chamfer the notch portion of the wafer as
shown in FIG. 5B. That is, as shown in FIG. 5B, it is possible to
form a disk-shaped grindstone 8 which comprises first and second
disk-shaped grindstone members 8a and 8b. The first disk-shaped
grindstone member 8a has a flat portion 2 for chamfering the
circumferential portion 6. The second disk-shaped grindstone member
8b is attached to the first disk-shaped grindstone member 8a and
has an edge portion in the form of a shape mating with a part of
the notch so as to form a valley part of the notch portion.
However, it is also possible to form the first and second
disk-shaped grindstone member are integrally formed. In the
last-mentioned embodiment, when compared with the embodiment in
which the grindstone is used to chamfer the cylindrical portion of
the wafer and also to chamfer the notch portion thereof, the
grindstones can be effectively prevented from losing their shapes
which are made in the form of the edge portion of the wafer to be
chamfered.
[0060] The present invention is based on Japanese Patent
Application No. Hei. 10-101267 and Hei. 11-50348, which is
incorprated herein by reference.
[0061] While there has been described in connection with the
preferred embodiment of the invention, it will be obvious to those
skilled in the art that various changes and modifications may be
made therein without departing from the invention, and it is aimed,
therefore, to cover in the appended claim all such changes and
modifications as fall within the true spirit and scope of the
invention.
[0062] As described in an above-mentioned description, in a wafer
chamfering method according to the invention, since the peripheral
edge portion of the disk-shaped wafer is chamfered by the
disk-shaped grinding wheel under predetermined conditions, the
wafer chamfering method which can chamfer a surface of the wafer
into an arbitrary shape and in the same shape all the time with
excellent reproduction characteristics As has been described
heretofore, in a wafer chamfering method according to the
invention, since there is used the grindstone which includes a flat
portion and edge portions, the amount of abrasion of the grinding
surface of the grindstone can be decreased to a great extent to
thereby reduce the amount of loss of the shape of the grindstone.
Also, the shape of the grindstone and the arrangement of the
grindstone with respect to the wafer can reduce the influences that
could be otherwise caused by the shape-lost grindstone; and,
therefore, not only the same grindstone can be used to grind the
circumferential portion of the wafer as well as to chamber the
tapered notch portion of the wafer to thereby carry out a series of
chamfering operations without replacing the grindstone, but also
the same grindstone can be used for a long period of time without
dressing/re-shaping the grinding surface thereof. Further, since
the above-mentioned manner of use of the grindstone eliminates the
need to mold the grindstone in a thin shape, the grindstone can be
used as a grindstone having a large diameter and, therefore, even
if the grindstone is rotated at a low rotation speed, there can be
obtained a high peripheral speed. In other words, when compared
with a case in which a grindstone having a small diameter,
according to the invention, a higher peripheral speed can be
obtained when the grindstone is rotated at the same speed as the
small-diameter grindstone, thereby being able to extend the life of
the grindstone.
[0063] In addition, in a wafer chamfering method according to the
invention, there can be provided an effect which is advantageous in
cost. That is, the circumferential portion and notch portion of the
wafer can be respectively chamfered in a mirror-like surface and
also, when compared with the embodiment in which the grindstone is
used to chamfer both of the circumferential portion and notch
portion of the wafer, the amount of abrasion of the edge portion of
the grindstone can be reduced, which in turn makes it possible to
reduce the cost of the grindstone.
[0064] Further, in a wafer chamfering method according to the
invention, there can be provided an outstanding effect: that is,
the wafer can be chamfered in a mirror-like surface shape as well
as in an arbitrary shape and in the same shape all the time by a
grinding operation which is low in cost but high in efficiency.
[0065] Furthermore, in a wafer chamfering method according to the
inventions, besides the above-mentioned effects of the invention,
there can also be provided another outstanding effect: that is, the
occurrence of the radially extending grinding streaks on the wafer
can be prevented effectively and thus the damage of the wafer such
as a crack or the like can be prevented effectively.
[0066] Moreover, in a wafer chamfering method according to the
invention, besides the above-mentioned effects of the invention,
there can also be provided still another outstanding effect: that
is, the peripheral edge portion and end face of the wafer can be
ground at a time in a mirror-surface shape.
* * * * *